Recently, there have been developed amorphous metal alloys having excellent magnetic properties. In order to utilize such properties effectively, there has been proposed an application of amorphous metal alloys to the magnetic core of a transformer or the like (See, for instance JP-A No. 115805/1983).
As is disclosed in the reference cited, a magnetic core is formed of a coiled strip material of an amorphous metal alloy having a very thin thickness. Such a magnetic core has an advantage in that the magnetic energy loss can be reduced considerably when compared with that of a conventional magnetic core made of steel. However, there is a disadvantage in that it is difficult to manufacture the magnetic core since it should be annealed in an inert gas of about 400.degree. C. applying magnetic field thereto.
Conventional method for annealing the magnetic core in the magnetic field are as follows;
first, a coil for magnetizing the magnetic core is wound around the latter, and, thereafter, each core is charged into an annealing furnace together with the magnetizing coil. After evacuation of gas in the furnace, inert gas is introduced thereinto and the temperature in the furnace is raised to a predetermined temperature to anneal the core in magnetic field being generated by the magnetizing coil.
However, the conventional method mentioned above has a disadvantage in that treatments therefor are troublesome since magnetizing coils are respectively wound around every magnetic core. Further, cost for annealing treatment becomes high since it is necessary to use an electrically conductive wire material covered with a heat proof insulating material as the magnetizing coil.
Contrary to the above, there is also proposed another annealing method in which a plurality of magnetic cores are fitted to a common magnetizing shaft made of electrically conductive material and are annealed in the magnetic field generated by supplying an appropriate current to the shaft.
These conventional methods mentioned above are essentially so called "batch process". Therefore, it is impossible to obtain annealed cores continuously. Moreover, thermal efficiency of the annealing furnace is very low as is easily understood by those skilled in the art.